1. Field of the Invention
The present invention relates to a control device of an alternator, and particularly to a control device of an alternator, which controls a generated voltage of the alternator by an ON/OFF duty ratio of applied voltage to an exciting coil, and which is suitably used for, for example, a vehicle.
2. Description of the Related Art
Conventionally, with respect to feedback control of a generated voltage of an alternator to a target voltage, Japanese Patent Application Laid-open No. Hei 05-176477 discloses a control device of an alternator in which an attempt to achieve such control is made by means of digital control using a microcomputer.
In this kind of conventional control device of an alternator, in the case where feedback control is carried out by making a generated voltage of the alternator follow a target voltage, after a target exciting current corresponding to a target generating current of the alternator is calculated through an equation based on the power generation characteristics of the alternator, an estimated exciting current which may actually flow is calculated through an equation based on the electromagnetic specification of the alternator.
Then, the target exciting current based on a deviation of the value of the target exciting current obtained by this calculation from the value of the estimated exciting current is subjected to first order lead correction based on the power generation characteristics of the alternator and the electromagnetic specification (for example, number of turns of an exciting winding constituting the alternator, etc.), and a control exciting current is calculated.
Next, an ON/OFF duty ratio to the control exciting current determined by the calculation is selected and is read out from a memory including a table previously set on the basis of the electromagnetic specification of the alternator. On the basis of the ON/OFF duty ratio read out from this memory, an applied voltage to an exciting coil is controlled.
In the conventional control apparatus of an alternator constructed as described above, in the case where the power generation characteristics or electromagnetic specification of the alternator is changed or in the case where the control device is applied to an alternator having different electromagnetic specification and power generation characteristics, in the control device, it is necessary to change the table of the ON/OFF duty ratio to control the exciting current and the coefficients of calculation equations of the exciting current for every electromagnetic specification and power generation characteristics of the alternator, and to again take matching. Thus, there has been a problem that the correcting work is troublesome and it takes a long time.